From 6fc0e58e30b8f7b99ebdc0ace718e195aae3df91 Mon Sep 17 00:00:00 2001
From: Andrea Spagnolo <aspagnolo@vmware.com>
Date: Fri, 26 Jun 2020 22:01:28 +0200
Subject: [PATCH] Add ObservedGeneration to MachinePool Controller

Signed-off-by: Andrea Spagnolo <aspagnolo@vmware.com>
---
 exp/api/v1alpha3/machinepool_types.go          | 4 ++++
 exp/controllers/machinepool_controller.go      | 7 ++++++-
 exp/controllers/machinepool_controller_test.go | 2 ++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/exp/api/v1alpha3/machinepool_types.go b/exp/api/v1alpha3/machinepool_types.go
index b7db1a28698b..9e392dd2f2f8 100644
--- a/exp/api/v1alpha3/machinepool_types.go
+++ b/exp/api/v1alpha3/machinepool_types.go
@@ -116,6 +116,10 @@ type MachinePoolStatus struct {
 	// InfrastructureReady is the state of the infrastructure provider.
 	// +optional
 	InfrastructureReady bool `json:"infrastructureReady"`
+
+	// ObservedGeneration is the latest generation observed by the controller.
+	// +optional
+	ObservedGeneration int64 `json:"observedGeneration,omitempty"`
 }
 
 // ANCHOR_END: MachinePoolStatus
diff --git a/exp/controllers/machinepool_controller.go b/exp/controllers/machinepool_controller.go
index 42cb90957d7a..263d6926a0f4 100644
--- a/exp/controllers/machinepool_controller.go
+++ b/exp/controllers/machinepool_controller.go
@@ -137,7 +137,12 @@ func (r *MachinePoolReconciler) Reconcile(req ctrl.Request) (_ ctrl.Result, rete
 		// TODO(jpang): add support for metrics.
 
 		// Always attempt to patch the object and status after each reconciliation.
-		if err := patchHelper.Patch(ctx, mp); err != nil {
+		// Patch ObservedGeneration only if the reconciliation completed successfully
+		patchOpts := []patch.Option{}
+		if reterr == nil {
+			patchOpts = append(patchOpts, patch.WithStatusObservedGeneration{})
+		}
+		if err := patchHelper.Patch(ctx, mp, patchOpts...); err != nil {
 			reterr = kerrors.NewAggregate([]error{reterr, err})
 		}
 	}()
diff --git a/exp/controllers/machinepool_controller_test.go b/exp/controllers/machinepool_controller_test.go
index f81914b6ef17..991e402de755 100644
--- a/exp/controllers/machinepool_controller_test.go
+++ b/exp/controllers/machinepool_controller_test.go
@@ -337,6 +337,7 @@ func TestReconcileMachinePoolRequest(t *testing.T) {
 					NodeRefs: []corev1.ObjectReference{
 						{Name: "test"},
 					},
+					ObservedGeneration: 1,
 				},
 			},
 			expected: expected{
@@ -372,6 +373,7 @@ func TestReconcileMachinePoolRequest(t *testing.T) {
 					NodeRefs: []corev1.ObjectReference{
 						{Name: "test"},
 					},
+					ObservedGeneration: 1,
 				},
 			},
 			expected: expected{